Transcript 1.5
Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? 1.5 09 How do plate movements create hazards? Part A Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? What is the distribution pattern of tectonic What is in common hazards? about the distribution of the tectonic hazards shown on the map? Find out the world distribution of tectonic hazards GIS. They by areusing found Please click Distribution of tectonic hazards in early July 2007 09 to browse online along the plate boundaries. Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? What is the distribution pattern of tectonic hazards? Destructive plate boundaries Constructive plate boundaries Conservative plate boundaries Frequent Not frequent Frequent Earthquakes 09 Others East Africa Volcanic eruptions Frequent in the CircumPacific Belt Mainly under the sea East Africa, the Atlantic and the Hawaiian Islands Tsunamis Frequent in the Pacific Not frequent / Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why do most tectonic hazards occur at plate boundaries? 1 Earthquakes Friction is greater at __________ conservative destructive and ____________ plate boundaries, therefore higher pressure is built up. Asthenosphere Plates collide AsAsthenosphere a result, earthquakes are Plates diverge stronger and more frequent there. When the pressure in the plates exceeds How the do strength of the rock, the rock ______ breaks and plates move? _________. displaces The land shakes. Asthenosphere Plates slide past each other 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why do most tectonic hazards occur at plate boundaries? 2 Volcanic eruptions At destructive plate boundaries Plate subducts and melts below the subduction zone. Pressure is intensified Compressional force Asthenosphere 09 Release of pressure causes volcanic eruptions Subduction causes cracks within the crust Magma rises up through cracks Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why do most tectonic hazards occur at plate boundaries? 2 Volcanic eruptions At constructive plate boundaries under water Great water pressure at the sea bottom suppresses volcanic activity Gap opens in the crust Tensional force Asthenosphere 09 Lava wells out slowly to fill the gap Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why do most tectonic hazards occur at plate boundaries? The following sudden vertical 3 Tsunamis movements of a large area of sea floor cause tsunamis: Shallow focus associated with vertical displacement of rock Submarine landslide Submarine volcanic eruptions Submarine earthquake Asthenosphere 09 Quit Part 1 3 Opportunities and risks─Is it rational to live in hazard-prone areas? Tsunamis The three causes of tsunamis are usually found at destructive plate boundaries. Therefore, the Pacific Ocean is vulnerable to the attack of tsunamis. The pink lines indicate How the time longrequired did the 1960 for and tsunamis 1946 tsunamis formed take along to reach these Honolulu lines to reach respectively? the Hawaiian Islands. 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why do most tectonic hazards occur at plate boundaries? 3 Tsunamis Even Southwas Asian Thethe tsunami tsunami 2004 was caused byin the collision taken place at a of the Indo-Australian destructive plate Plate and the Eurasian boundary. Plate. Origin of the South Asian tsunami 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why are some earthquake and volcanic zones far away from plate boundaries? The Hawaiian Islands are not located at plate boundaries. Why are there earthquakes and volcanic eruptions? 09 Hawaiian Islands Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why are some earthquake and volcanic zones far away from plate boundaries? 1 Hot spot 1 1 2 1 23 As the plate The Hawaiian moves with the Islands are convection located above a The location of currents below, hot spot the hot spot is the volcanoes beneath the fixed. formed are Pacific Plate. carried away together with the moving plate. Note: the number represents the sequence of volcanoes formed 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why are some earthquake and volcanic zones far away from plate boundaries? 1 Hot spot How does the alignment of the Hawaiian Islands indicate the direction of plate movements? Hot spot 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why are some earthquake and volcanic zones far away from plate boundaries? 1 Hot spot Hot spots that are active in the last 10 million years Hot spots do not show any specific pattern. Most of them lie at a distance from the plate boundaries. 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why are some earthquake and volcanic zones far away from plate boundaries? 2 New convection currents of magma develops New currents of magma in the asthenosphere Thereconvection are some uncertain plate boundaries with may develop. A plate can crack and break up further associated earthquakes. along new plate boundaries. 09 Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? Why are some earthquake and volcanic zones far away from plate boundaries? 3 Tensional force Relative movement In East Africa, the African Plate is breaking up under tensional force. Faults Earthquakes African Plate (Nubian) Tensional force Magma currents diverge Asthenosphere Cross-section of the East African Rift 09 African Plate (Somalian) Along the fault planes, the central block is sinking between two splitting plates. Friction accumulated at the fault plane causes earthquakes. Quit Part 1 Opportunities and risks─Is it rational to live in hazard-prone areas? After studying the spatial distribution and reasons for earthquakes, volcanic eruptions and tsunamis, we will explore the destructive effects caused by these tectonic hazards in Part B. 09 Quit Part 1 3 Opportunities and risks─Is it rational to live in hazard-prone areas? Tsunamis How does a tsunami work? Animation 1-5-1e.mpg NSS eBook Part 1 Unit 1.5 (Tsunami: How does it work?: 01_e_ani_01.mpg) Please click above for animation 09 Quit